Iran's Youth Correspondents Club news agency reported on its Telegram channel that websites linked to Tehran municipality were suspended On Thursday, citing possible infiltration.
Iran's exiled opposition Group of People's Mujahedeen said it had disabled surveillance cameras in Tehran, the Associated Press reported.
The People's Mujahedeen aired a video showing the hacking of the Tehran municipality's website, and other sites featuring critical drawings of Khomeini.
A picture of Ayatollah Ali Khamenei with a red X on his face, as well as pictures of the leaders of the People's Mujahedeen, Massoud Rajavi and his wife Maryam Rajavi, and words calling for an uprising were posted on one of these sites.
"A deliberate malfunction in tehran's internal systems, including the publication of a humiliating image, kept this system out of reach of colleagues for a few minutes," the young correspondents' club agency quoted the municipality as saying.
The agency said the municipality's website was suspended, adding that a group of hackers posted video recordings from the municipal data center, claiming to have taken control of the capital's surveillance cameras.
The Iranian authorities will conduct investigations to find out who is behind this and will publish the information after the final review, the agency said.
In the context of cyber threats between Iran and the West, FBI Director Christopher Wray confirmed Wednesday that Iranian government-backed hackers tried to target a children's hospital in the United States, noting that they backed away from their plan as soon as the Americans learned of it.
"In the summer of 2021, iranian government-sponsored hackers tried to carry out one of the most hateful cyberattacks I've ever seen, when they tried to target Boston Childers Hospital," Ray said in a speech at Boston College on cyber threats.
He said U.S. authorities have received a tip from an intelligence partner that the hospital is about to be attacked.
"CyberSquad from our Boston office was quick to warn the hospital. Immediately, we were able to help him identify the threat and then reduce it."
Ray did not provide details about which branch of the Iranian government was behind the threat, nor did he say how the attack would have affected the hospital if it had been carried out.
He said the cyberattack, which he described as "disgraceful," endangered the services provided to patients at this renowned hospital.